X-ray specular-reflectivity study of the liquid-vapor density profile ofHe4

Abstract

1993. X-ray specularreflectivity study of the liquid-vapor density profile of \(^4\)He. Physical Review B 48(13): 9644-9659.

Thickness Measurements of Thin Perfluoropolyether Polymer Films on Silicon and Amorphous-Hydrogenated Carbon with X-Ray Reflectivity, ESCA and Optical Ellipsometry

“…The model incorporates several variable parameters-film thickness, density, and roughness-which are fitted to the data. For any interface, the roughness can take many forms, but a Gaussian roughness distribution (error function density profile) is typically assumed (16,17,24,25), although other forms are also reported (26,27). In this work, we tried several forms for the roughness and, in each case described below, we report the form that provides the best fit to the data.…”

“…Specifically, we used a slightly asymmetric sech interface profile with η ≈ −0.5 in the notation of Ref. (26,27). This is probably due to the adsorbed hydrocarbon contamination (16,17,33), but could also be a real manifestation of the surface roughness.…”

Free surface of superfluidHe4at zero temperature

“…This feature is directly related to the possible asymmetry of ͑z͒. 17,18,20 In order to guide our analysis on this point, and trying to be quantitatively accurate, we have fitted to the DMC data functions of the type…”

“…3,[15][16][17][18] The most direct information on the density profile and interfacial width has been obtained by x-ray reflectivity [19][20][21] and ellipsometric 22 measurements. The latter was carried out by Osborne,22 who assuming a Fermi function for the profile, extracted a 10-90 % width of 9.4 Å at 1.8 K. The most recent data correspond to the x-ray measurement of Penanen et al 21 who reported a value 6.5 Å at 0.45 K, a lower temperature than the first measure performed by Lurio et al 20 at 1.13 K who reported a wider surface of 9.1 Å. The relative spread of the experimental results on the microscopic characteristics of the density profile points out the difficulties which experimental setups face to carry out a clean extraction of the data and its reduction to the ground state, i.e., to zero temperature.…”

Structure of LargeH3e−H4Pí1, Mayol2, Barranco3 1999Phys. Rev. Lett.530430View full textAdd to dashboardCite

“…In the case of drops made of up to several thousand atoms, the surface region constitutes a sizeable part of the system [13], and the surface has a large capacity for storing 3 He atoms before they get inside the drop [14]. Because of the wide free surface of both isotopes [15,16] and the low surface tension of the 3 He-4 He liquid interface [17], one expects that this region plays a prominent role when it constitutes a large part of the system or, as in the present case, when it is close to the dopant atom or molecule.The structure and energetics of mixed, doped or not, helium droplets have been addressed using a finite-range density functional method [14]. That work was carried out before the experiments reported in Ref.…”